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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3ecdcbc246ea23cfc5ead889a5da4ee6f18a617c5714907a8b43455de6b5f844' 
  AND token = '/4sMGDYJmLRG+zle2PuK/D3FjwTaPkGYNdV42muzwGc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00014

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}